"Determine how much content to include on each page.* Be sure that if a searcher came directly to this page, they could easily find the exact item they wanted (e.g., without lots of scrolling before locating the desired content).* Maintain reasonable page load time."

I don' t think it is strange, it is annoying if you've got to scroll through 15 pages of infinite scroll to find the thing of interest.

To me this is no different than frustrating users by having content sitting behind tabbed UI, someone lands on the page from search and can't find what they were looking for immediately as the content is sitting behind a tab – it's frustrating for users.

If I follow a link to a category page on pinterest about tattoos, I want to be able to find the images of interest relevant to the link.

Most people that implement infinite scrolling don't update the browser URL as you scroll down the page, so that if they shared a URL – they are actually sharing page 13 for example instead of the base category URL.

That's pretty much the way I see it too. I've seen too many e-commerce sites get so fixated on what a great thing infinite scroll is, that they never consider all the bolt-ons they'll need (comparators, wishlists, vertical bookmarks, whatnot) in order to actually turn the browsers into buyers without frustrating the crepe out of them.